The lungs have unique, dual circulatory systems. The pulmonary circulatory system has the ability to accommodate large volumes of blood at low pressure and brings deoxygenated blood from the right ventricle to the gas-exchanging units in the lung. The exchange.Inlungdiseasethatinvolvesscarformation(i.e.,pulmonaryfibrosis),thetotallungvolumedecreasesasaresultofthelossofalveoliandimpairmentofO2diffusionintothecapillariesbyathickened,nonpermeablematrix.Historically,idiopathicpulmonaryfibrosishasbeenverydifficulttotreatbecauseofthelackofspecifictherapeutics,whichcaninhibitcollagendeposition.Twotherapeuticcompounds(pirfenidoneandnintedanib)havebeenshowninclinicaltrialstoslowtheprogressionofthediseaseandimproveoutcomesinpatientswithidiopathicpulmonaryfibrosis.Pirfenidoneisasmalllow-molecular-weightcompoundwithanti-inflammatoryproperties(itdecreasesprocollagentypesIandIIsynthesis),andnintedanibisatyrosinekinaseinhibitor(inhibitsvascularendothelialgrowthfactorandfibroblast-derivedgrowthfactor).
bronchial circulation arises from the aorta and provides nourishment (O2) to the lung parenchyma.
5.
Breathing is automatic; the lungs are innervated by the autonomic nervous system of the PNS while under the control of the CNS. Parasympathetic stimulation results in constriction of airway smooth muscles (airway narrowing) whereas sympathetic stimulation results in relaxation of airway smooth muscles (airway opening).
6.
Inspiration is the active phase of breathing. The diaphragm is the major muscle of respiration, and its contraction creates a pressure difference (mechanoreceptor response) between the thorax and diaphragm (negative pressure in the chest), which induces inspiration.
7.
The respiratory center is located in the medulla and regulates respiration with input from sensory (mechanoreceptor and chemoreceptor) feedback loops.
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Upon completion of this chapter, the student should be able to answer the following questions: 1.
Define the different pressures in the respiratory system.
2.
Explain how a pressure gradient is created.
3.